The present invention relates to a light source device for use in an image forming apparatus and using a semiconductor laser.
A digital copier, laser printer, facsimile apparatus or similar image forming apparatus extensively used today included a light source device having a semiconductor laser and a collimator lens. Optical characteristics required of the light source device include the directivity of laser light (optical axis characteristic) and the parallelism of a beam (collimation characteristic). To meet these requirements, it is a common practive to adjust the relative position of the emission point of the laser and the collimator lens in the directions of three axes (x, y and z). The positional accuracy is severely restricted to below the order of microns. Therefore, the device using the laser and collimator lens must be capable of being adjusted in the three axis directions and then fixed at its adjusted position.
When the collimator lens is fixed in place by adhesive, the adhesive contracts in the event of setting. It is therefore necessary to reduce the influence of the contraction on the optical characteristics as far as possible. Particularly, high accuracy is required of the device in the direction z (optical axis direction), so that the contraction should preferably be prevented from occurring in the direction z. For this purpose, the adhesive layer should preferably extend substantially parallel to the optical axis (axis z). Also, the contraction should preferably be limited to one of the directions x and y in order to facilitate adjustment even in such a direction.
Light source devices each having a semiconductor laser and a collimator lens are taught in, e.g., Japanese Patent Laid-Open Publication Nos. 5-88061, 5-136952, and 5-273483. However, the conventional devices of the type described have some problems yet to be solved, as follows:
(1) Each device needs a number of constituent parts which increase the cost.
(2) The constituent parts are dislocated in the directions x, y and z in the event of assembly, so that the directivity (optical axis characteristic) of the laser is deteriorated.
(3) Use cannot be made of ultraviolet light curable adhesive for fixing the collimator lens in place. This kind of adhesive can set in a short period of time in a desired manner and is highly reliable.
The conventional devices have other problems which will be described, in addition to the above problems.
It is therefore an object of the present invention to provide an inexpensive and highly accurate light source device needing a minimum number of constituent parts, protecting the individual part from dislocation during assembly, and allowing a collimator lens to be fixed in place by photo-curable adhesive.
In accordance with the present invention, a light source device has a flat base member having a through bore. A semiconductor laser for emitting laser light is mounted on the rear of the base member and fitted in the through bore. A lens is mounted on the front of the base member at the front of the through bore and coaxial with the optical axis of the semiconductor laser. A lens support member is positioned at the front of the through bore coaxially with the optical axis of the semiconductor laser. The lens support member has an arcuate section and a diameter slightly greater than the outside diameter of the lens. The lens is affixed to the lens support member by photo-curable adhesive.
Also, in accordance with the present invention, a light source device has a base member having a through bore substantially at the center thereof. A semiconductor laser is fitted in the through bore for emitting laser light. A lens is mounted on the surface of the base member. A lens support member supports the lens positioned in the directions of three axes with adhesive filling a clearance between the lens and the surface of the base member.
Further, in accordance with the present invention, a light source device has a semiconductor laser for emitting laser light, a first support member supporting the semiconductor laser, a lens positioned coaxially with the optical axis of the semiconductor laser, and a second support member supporting the lens. The first support member has a first reference surface perpendicular to the optical axis of the semiconductor laser. The second support member has a second reference surface parallel to the optical axis of the semiconductor laser.
Moreover, in accordance with the present invention, a light source device has a semiconductor laser for emitting laser light, a first support member supporting the semiconductor laser, a lens positioned coaxially with the optical axis of the semiconductor laser, a second support member supporting the lens, an aperture forming member having an aperture for shaping the laser light issuing from the semiconductor laser, and a third support member supporting the aperture forming member on the second support member from below the second support member. The first support member is positioned perpendicularly to the optical axis while the second support member is located in front of the first support member.